In a pumping fluid well, such as an oil well, the oil from the well formation flows into a well conduit such as a casing and to the pump where it is then pumped to the well surface. However, it is sometimes desirable to shut off the flow of oil from the formation into the conduit, such as during workover operations. That is, with the pump turned off the oil from the formation will continue to flow into the conduit and rise therein and interfere with workover operations.
Therefore, one feature of the present invention is to provide a safety valve to shut off the flow of a well fluid in a well being produced by a pump, and more specifically, the present invention is directed to controlling a well safety valve by the fluid level in the well conduit. The fluid level in a well is lower when the pump is being operated than the level when pumping is stopped. That is, when the well pump is stopped, the fluid in the well conduit around the pump begins to rise and accumulate. The present invention uses the differences in the fluid level before and after pumping, which provides different hydrostatic heads which control the safety valve.